Point mutations in the beta-tubulin gene conferred carbendazim-resistant phenotypes of Colletotrichum gloeosporioides causing 'Nam Dok Mai' mango anthracnose.
Nalumpang S., Miyamoto Y., Miyake C., Izumi Y., Akitmitsu K., Kongtragoul P.
Author Affiliation: Department of Entomology and Plant Pathology, Faculty of Agriculture, Chiang Mai University, Chiang Mai, Thailand.
International Journal of Agricultural Technology 6 : 365-378
Abstract : Fifty-nine naturally-infected isolates of Colletotrichum gloeosporioides causing 'Nam Dok Mai' mango anthracnose disease were collected from markets and orchards in Thailand; consisting of 6 isolates (10.17%) from leaves and 53 isolates (89.83%) from fruits. In preliminary studies conducted in vitro with potato dextrose agar amended with carbendazim at various concentrations: 0.1, 1, 10, 100, 500 and 1,000 mg/l. The phenotype-resistant levels evaluation was grouping into four representative phenotypes of reactions as highly resistance (HR; ?500 mg/l), moderately resistance (MR; ?100 mg/l), weakly resistance (WR; ?10 mg/l) and sensitive (S; ?1 mg/l). The result showed 49 isolates (83.05%) were HR phenotypes; consisting of 2 isolates (3.39%) from leaves and 47 isolates (79.66%) from fruits, and 10 isolates (16.95%) were S phenotypes; consisting of 4 isolates (6.78%) from leaves and 6 isolates (10.22%) from fruits. The differences in the carbendazim-resistant phenotypes were conspicuous in sequence analysis of the second beta-tubulin (TUB2) gene compared with C. gloeosporioides f. sp. aeschynomene (accession No. U14138). HR phenotypes were revealed a single nucleotide mutation; an adenine (A) to cytosine (C) transversion, resulting in a substation of codon 198, which encodes glutamic acid (GAG) in S phenotypes, was converted to a codon for alanine (GCG) which is closely associated with conferring carbendazim-resistant phenotype. This indicates that careful management of carbendazim fungicides applications is necessary to achieve effective control.